Electric detonator



1965 H. A. G. PASTERNACK 3,283,716

ELECTRIC DETONATOR Filed Dec. 6, 1963 INVENTOR- /$04r1 5. as/er e c If United States Patent 3,283,716 ELECTRIC DETONATOR Horst A. G. Iasternack, Essen, Germany, assignor to Wasag-Chemie Aktiengesellschaft, Essen, Germany Filed Dec. 6, 1963, Ser. No. 328,689 Claims priority, application Germany, Dec. 12, 1962, W 33.502 2 Claims. (Cl. 10228) The present invention relates to an electric igniting element or detonator with an inner electrode and an outer electrode which surrounds an insulating body and has a contact part arranged at one of its edges, said contact part engaging a metalized surface at one end face of said insulating body. It is at the contact point between the contact part and the metalized surface which latter is in contact with the inner electrode, that the igniting spark for igniting or detonating the initiating explosive charge will occur.

The invention furthermore concerns a method of varying the electric resistance of detonators of the above mentioned type when making the same.

With the heretofore known electric igniting element or detonator of the above mentioned general type, the contact part is designed in the form of a plate-shaped tongue of a marginal portion of the outer electrode, which portion is folded over to the edge of the end face of the insulating body. This plate-shaped tongue or tip preferably rests against a conical or pyramid-shaped surface of one end face of the insulating body, which conical or pyramid-shaped surface tapers along a straight, concave or convex line.

While this igniting element or detonator has proved generally successful, it was necessary with this known igniting element or detonator to meet the following requirements very carefully in order to assure the function of the ignition element or detonator or to maintain the desired values. In this connection, it is to be noted that, first of all, care had to be taken that only the tip of the plate-shaped tongue contacts the metalized surface at one end face of the insulating body. Furthermore, it was necessary to press the insulating body into the cylindrical outer electrode at a certain pressure acting in longitudinal direction. If this last mentioned requirement was not met, the tip of the plate-shaped tongue did not produce a point contact with the metalized end face of the insulating body.

If both of the said requirements, which operatively are closely related to each other, had not been met, the initiating or detonating explosive charge could not be brought into the required neighborhood of the spark, or expressed differently, an undesired electric resistance of the detonator was created.

An electric igniting element or detonator, furthermore, has to meet the requirement that the initiating or detonating explosive charge will be pressed at high pressure against the corresponding parts of the outer electrode and against the insulating body.

It is, therefore, an object of the present invention to overcome the above mentioned drawbacks.

It is another object of this invention to provide an electric igniting element or detonator which will assure uniform resistance values.

It is a further object of this invention to permit a variation of the resistance values within certain limits.

It is also an object of this invention to permit the application of a very high pressure for pressing the initiating or detonating explosive charge against the insulating body.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing, in which:

3,283,7l6 Patented Nov. 8, 1966 FIG. 1 represents a vertical section through a detonator according to the present invention.

FIG. 2 is a section taken along the line IIII of FIG. 1.

FIG. 3 is a top view of the detonator of FIG. 1.

FIGS. 4 and 5 illustrate on a somewhat larger scale than FIG. 1 certain details thereof.

The electric detonator according to the present invention is characterized primarily in that the outer electrode together with a cylindrical margial portion thereof forms a gable-shaped depression the tip of which rests against a metalized surface of one end face of the insulating body. The design of the insulating body, of the partially metalized end surface, and of the metalized inner bore for receiving the tubular inner electrode may be of any standard type.

Preferably, the cylindrical marginal portion of the outer electrode should, at least at the gable-shaped depression, be free from burrs or the like.

The metalized end face of the insulating body may in a manner known per se be provided with a conical or pyramid-shaped extension against which the tip of the gable-shaped depression will rest. Inasmuch as the resistance of the igniting element in addition to depending on the specific resistance of the material being employed also depends on the cross section and the length of the conductor, the resistance of the igniting element or detonator may be varied by pressing the insulating body at a higher or lower pressure in longitudinal direction into the outer electrode. When employing high pressures, the tip will slide along the conical or pyramid-shaped end face of the insulating body without sacrificing the point contact of the depression with the metalized surface while the effective length of the metalized surface serving as conductor will be increased. When employing a low pressure, the tip of the depression will remain closer to the pyramid-shaped or conical tip of the end face of the insulating body whereby the conducting path or effective length of the metalized surface will be shorter and the resistance will be lower. In this connection, it is advantageous in the area around the tip of the depression to design the metallic end surface layer of the insulating body uniformly so that there will be obtained a linear increase in the resistance of the element with linear increase in the pressures at which the insulating body is pressed into the outer electrode. However, it is also possible to design the metallic surface layer at the end face with different thicknesses.

Referring now to the drawing in detail, the insulating body 1 made of any suitable insulating material as for instance a ceramic material has a central longitudinal bore 2 the wall of which is covered by a metallic layer S, for instance a layer of a silver alloy, said layer extending along the entire length of bore 2 and over the conical extension 4 at one end portion (in the drawing the upper portion) of the insulating body up to the circular foot line 5 of conical extension 4. A sleeve 6 engages the metalized wall of said bore 2 and forms the inner electrode. This inner electrode may be made for instance of an aluminium-steel alloy. The shape of said inner electrode 6 is such that it follows the contour of the bore 2 including the tapering portion thereof.

The insulating body 1 has been pressed in the direction of the arrow P into a cylindrical metal sleeve 7 which forms the outer electrode. This outer electrode may be made for instance of an alutmimlm-steel alloy. After the insulating body 1 has thus been pressed into the cylindrical metal sleeve 7, the said insulating body is covered at the bottom end face by a layer 8 of an adhesive for metals which forms an adhesive layer and enters between the insulating body 1 and inner electrode 6 and also between the insulating body 1 and the outer elect-rode 7 thereby additionally holding these members in their respective position. The outer electrode 7 comprises a cylindrical section 9 having a wall protruding longitudinally beyond the conical portion of the insulatin g body 1. The marginal edge 9a of the outer electrode 7 is free from burrs and the like. A portion of this wall is depressed longitudinally and extends inwardly toward the center and is shaped so as to have the form of an inwardly directed gable-like depression V-shape, in cross section, the tip 11 of which has point contact with the metalized surface S of the conical portion 4 of the insulating body 1. The two leg on walls 12, 13 of said gable-like depression impart upon the latter a high mechanical strength so that it will be possible not only to press the insulating body 1 in the direction of the arrow P at a more or less high pressure into the outer electrode 7 without affecting the point contact .at point 11, but also to press the initiating explosive charge in the direction of the arrow Z at a high pressure against the igniting element without causing any material deformation of the depression acting as contact part.

The metal layer S as illustrated in FIG. 4 may, at the upper edge R of cone 4 and in the immediate vicinity thereof, form a layer section s which is somewhat thicker than at the foot line 5 of the cone or at the wall of bore 2. Preferably, however, as illustrated in FIG. 5, the layer S at the inclined section A of the cone will be given a uniform thickness. It will be appreciated that the tip 10a of the depression can relatively slide along the said section A whereby the distance from said tip to the contact of the inner electrode 6 with the layer S will be increased or decreased depending on the relative downward or upward movement of tip 10a with regard to the inclined section A. It is thus possible also to increase the resistance when tip 10a moves into the position 10a indicated by dash lines. This is brought about by increasing the pressure acting in the direction of the anrow P at which the insulating :body 1 is pressed into the outer electrode 7. In this way, it is possible to produce different resistances of detonators by pressing the respective insulating bodies at different pressures into the cylindrical outer electrodes.

As will be evident, particularly from FIG. 5, the depressed edge or gable portion K fronts a line along the apex and may extend inwardly at any angle relative to a plane transverse of the outer electrode, as much as 30 on either side of the plane.

As will be evident from the above, the design of the contact part as gable-shaped depression will produce a high mechanical strength at reduced cost of manufacture. The increased mechanical strength makes it possible to press the initiating explosive charge at high pressure against the contact part without deflecting or distorting the contact part and therefore without sacrificing the point contact between the contact part and the metalized portion of the end face surface of the insulating body. In View of the increased pressure at which the initiating explosive charge may be pressed against the contact part, and at which the insulating part is pressed in, the detonator will be made safe against premature or delayed action.

It is, of course, to be understood that the present invention is, by no means, limited to the particular structural features referred to above but may also comprise any modification within the scope of the appended claims.

What I claim is:

1. An electric igniting element for use in a detonator, which includes: an insulating body having two end faces and having a bore therethrough extending from one end face to the other end face of said insulating body, one of said end faces having a conical portion surrounding said bore, a metallic layer on the wall of said bore and on said conical portion, an inner electrode firmly located in said bore and in contact with said metallic layer, and an outer tubular electrode firmly surrounding and engaging said insulating body and having its wall protruding longitudinally from said insulating body beyond said conical face portion, said protruding portion of said wall being depressed inwardly and longitudinally at one point to form a depressed portion V-shape in cross section having the line of the apex extending inwardly from the wall of said tubular electrode to-a point in contact with said conical portion, the walls of said V-shape portion extending from said line of the apex outwardly and longitudinally to the tubular wall and the inward ends of said walls joining the point in contact with the end of said wall of said tubular electrode beyond said conical face portion.

2. An element as defined in claim 1, in which the line of the apex of the depressed portion forms an angle of not more than 30 with a plane perpendicular to the axis of said'tubular electrode.

References Cited by the Examiner UNITED STATES PATENTS 2,974,591 3/ 1961 Pasternack l0228 2,986,090 5/1961 Doe-rpinghaus 10228 FOREIGN PATENTS 1,153,445 10/ 1957 France. 1,021,774 12/1957 Germany.

BENJAMIN A. BORCHELT, Primary Examiner.

R. V. LOTTMANN, V. R. PENDEGRASS,

Assistant Examiners. 

1. AN ELECTRIC IGNITING ELEMENT FOR USE IN A DETONATOR, WHICH INCLUDES: AN INSULATING BODY HAVING TWO END FACES AND HAVING A BORE THERETHROUGH EXTENDING FROM ONE END FACE TO THE OTHER END FACE OF SAID INSULATING BODY, ONE OF SAID END FACES HAVING A CONICAL PORTION SURROUNDING SAID BORE, A METALLIC LAYER ON THE WALL OF SAID BORE AND ON SAID CONICAL PORTION, AN INNER ELECTRODE FIRMLY LOCATED IN SAID BORE AND IN CONTACT WITH SAID METALLIC LAYER, AND AN OUTER TUBULAR ELECTRODE FIRMLY SURROUNDING AND ENGAGING SAID INSULATING BODY AND HAVING ITS WALL PROTRUDING LONGITUDINALLY FROM SAID INSULATING BODY BEYOND SAID CONICAL FACE PORTION, SAID PROTRUDING PORTION OF SAID WALL BEING DEPRESSED INWARDLY AND LONGITUDINALLY AT ONE POINT TO FORM A DEPRESSED PORTION V-SHAPED IN CROSS SECTION HAVING THE LINE OF THE APEX EXTENDING INWARDLY FROM THE WALL OF SAID TUBULAR ELECTRODE TO A POINT IN CONTACT WITH SAID CONICAL PORTION, THE WALLS OF SAID V-SHAPED PORTION EXTENDING FROM SAID LINE OF THE APEX OUTWARDLY AND LONGITUDINALLY TO THE TUBULAR WALL AND THE INWARD ENDS OF SAID WALLS JOINING THE POINT IN CONTACT WITH THE END OF SAID WALL OF SAID TUBULAR ELECTRODE BEYOND SAID CONICAL FACE PORTION. 